Telephone-exchange system



TELEPHONE EXCHANGE SYSTEM Filed Dec. 27, 1919 2 Sheets-Shae! 1 //7 ve/vfor:

Patented Nov. 11, 1924,

i inner. arnr n ARTHUR RAYNSFORD, OF NEW YORK, N. Y., .ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. "Y, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed December 27, 1919.

To all whom it may concern Be it known that I, ARTHUR Rnvnsrono, a citizen of the United States, residing at New York, in the county of New York, State of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to such systems in which trunk circuits between central offices are employed for establishing connections between telephone lines terminating at the difl'erent central oflices.

An object of this invention is the provision of improved signaling means for such systems.

Another object of the present invention is the production of an improved highly efficient trunking system for use between a toll switchboard and an automatic exchange.

In attaining the objects of this invention, an operators impulse sending device provided at the toll switchboard and common to the cord circuits of a position, is ren dered individual to any of the cord circuits of the position by the actuation of a switch individual to said cord circuits; the associated trunk extending from the switchboard to the automatic exchange consists of two sections inductively united by means of a repeating coil and herein termed inner and outer sections. Associated with the trunk circuit is an impulse responsive relay, which responds to impulses transmitted by the impulse sender over a portion of one of the talking conductors of the inner section of the trunk circuit, and which repeats the impulses received over the inner section, to the outer section thereby controlling the operation of automatic switches accessible to the outer section;

A; further feature consists in the provisien of supervisory means for indicating to the operator whether the selected line at the automatic exchange is busy or idle, whether the called station is being signalled, when the called station answers and when couvers'ation is completed. I

For a more complete understanding of the invention, reference may be had to the following description in connection with the accompanying drawings which illustrate an embodiment of the invention. Fig. 1 shows diagrammatically that part of the equip- Serial No. 347,765.

ment at the toll exchange and Fig. 2 that at the automatic exchange.

As shown in the drawings, a. trunk circuit C extends from a toll switchboard to an automatic exchange. At the toll switchboard there is provided a toll cord circuit B for establishing connections between the telephone line A and the trunk circuit C. For the purpose of transmitting impulses over the trunk circuit for controlling the switches at the automatic exchange, there is provided. for each operators position, an impulse sender S. Individual to each cord circuit there is provided a key such as 14, the actuation of which associates the impulse sender with that particular cord circuit. Telephone lines, such as F terminate at the automatic exchange and connection therewith is established over the trunk circuit C. For the sake of clearness a connector cir cuit E only has been shown at the automatic exchange, although it will be understood that a number of selectors, such as D, may be interposed between the trunk C and the connector F. Only one toll cord circuit B, one trunk circuit C and one tele phone line A are shown in the drawings it being understood that a plurality of such cord circuits, trunk circuits and telephone lines are provided in practice.

The toll operator having been advised that connection is desired between the toll line A (which may be connected with the cord circuit B in any desired well-known. manner) and telephone line F terminating at an automatic exchange, connection with which must be established by way of the trunk circuit C extending between the toll switchboard and the automatic exchange, tests the jack of trunk circuit-C in the wellknown manner and if idle inserts plug of the cord circuit B into jack 21 of the trunk circuit C. This renders trunk C busy and completes a circuit for relay 22 through the sleeves of the jack and plug, whereupon relay 22 attracts its armature and places a ground on conductor 25. Supervisoryrelay 10 of cord circuit B is thereupon energized thereby completing a circuit for and lighting supervisory lamp 15. The path for the energization of relay 10 may be traced as follows :grounded battery, winding of retardation coil 30, back contact and inner armature of relay 28, upper left-hand winding of repeating coil 27, tip of jack 21, tip of plug 20, upper normal contacts of ringing key 19, inner normal contacts of relay 18, resistance 16, winding of relay 10, resistance 17, outer normal contacts of relay 18,

lower normal contacts of ringing key 19, ring does not receive sufficient current through the winding of relay 10 to cause its energization. The operator then actuates locking key 14 which closes a circuit through relays 11 and 18 in series. Relay 11 operates, thus closing a circuit at its armature and front contact, leading to the operators telephone circuit to operate a relay therein (no-t shown). Relay18 is marginal and in series with relay 11 does not receive sufficient current to cause its energization. The operator may now actuate impulse sending device S, which is common to the. cord circuits at the operators position, preparatory to sending out the impulses necessary for selecting telephone line F. Upon the setting of the impulse sending device S, 011' normal contacts 12 close and remain closed during the entire movement of the sending device or until it returns to normal position, causing the energization of relay 1.8 through the shunting of relay 11. Relay 18 in operating disconnects the calling from the called end of cord circuit B and connects impulse sender S to the calling end. The setting of sender S also establishes a circuitfor the energization of relay 23 of trunk C over the following path :grounded battery, off-normal contacts 12 of sender S, left-hand alternate contacts of relay 18, lower normal contacts of ringing key 19, ring of plug 20, ring of jack 21, left-hand armature and back contact of relay 24, winding of relay 23, and front contact and armature of relay 22 to ground. Relay 23 upon energization opens at its inner left-hand armature and back contact, the circuit for ringing relay 31, thereby preventing this relay from operating during the sending of impulses. Relay 23, upon energization, completes a circuit at its inner right-hand armature and front contact for relay 34-, which locks up under the control of sleeve relay 22 through conductor 25. At its outer right hand armature and front contact relay 23 completes a circuit for relay 28, which upon energizing disconnects battery and ground from the trunk during the time in which the sender S is off normal. Relay 23, upon energization, also completes a circuit for an impulse responsive relay 35 over a path extending from grounded battery, interrupting contacts 13 of sender S, inner alternate con tacts of relay 18, upper normal contacts of ringing key 19, tip of plug 20, tip of jack 21, outer left-hand armature and alternate contacts of relay 23, and winding of relay 35 to ground. Relay 35 upon energization completes a circuit at its inner armature and front contact for slow-to release relay 36. It is thus seen that as the sending device returns to normal, impulse relay 35 will be intermittently deenergized a number of times according to the digit dialed due to its circuit being interrupted at contacts 13 of the sender. The impulse responsive relay 35 in responding to the impulses transmitted by the opening and closing of. contacts 13 of the impulse sending device S controls the usual motor magnets for the selector switch D, which is not shown since it forms no essential part of the present invention and which may be similar to the selector switch disclosed in the patent to lVillis, No. 1,315,442.

The selector switch D schematically indicated in Fig. 2 of the drawings is individual to the trunk circuit C and it will be assumed that in response to impulses transmitted by the sender S, trunk circuit C has been extended through selector D and connected to an idle connector The impulse sender S will then be actuated to send the impulses necessary to setthe connector upon the terminals of a subscribers line such as 1*. Upon the initial operation of sender S, impulse responsive relay 35 will be energized as heretofore described, there by completing a circuit for relay 111 of the connector 73 over the following path ground, outer right-hand armature and front contact of relay 35, back contact. righthand armature and. right-hand winding of relay 40, front contact and left-hand armature of relay 36, back contact and inner rigl'it-hand armature of relay 39, lower righ hand winding of repeating coil 27, brush 102, terminal 105, inner left-hand armature and back contact of relay 107, left-hand armature and back contact of relay 112,'and winding of relay 111 to grounded battery. A circuit will also be completed for impulse relay 109 over the following path :-ground, outer right-hand armature and front contact of relay 35, back contact, right-hand armature and left-hand winding of relay 40, back contact and outer right-hand armature of relay 39, upper right-hand winding of repeating coil 27, brush 101, terminal 104. outer left-hand armature and back contact of relay 107, and winding of relay 109 to grounded battery. Relay 40 being differentially wound does not become energized in this circuit. Relay 109 in energizing completes a circuit at its left-hand armature and front contact for slow-to, release relay 110.

Relay 110 upon energizing prepares a circuit at its inner armature and front contact for primary motor magnet 115 and at its outer armature and front contact places a ground upon terminal 1106, thereby rendering connector E busy.

Upon the first opening of impulse contacts 13 of sender S, as the sender returns to normal, impulse responsive relay releases and at its inner armature and back. contact completes a circuit for relay 38, said circuit extending through the right-hand armature and front contact of relay 36. Relay 38 is thereupon energized and locks up under the control of relay 23. Relay 38 upon attracting its armatures completes a di rect circuit for relays 109 and 111 of connector E. The circuit for relay 109 may be traced as follows :ground, outer armature, and front contact of relay 35, front contact and inner left-hand armature of relay 38 upper right-hand winding of repeating coil 27, brush 101, terminal 104, outer lef -hand armature and back contact of relay 107 Winding of relay 109 to grounded battery. Thecircuit for relay 111 may be traced as follows :ground, outer armature and front contact of relay 35, front contact and outer left-hand armature of relay 38, lower righthand winding of repeating coil 2?, brush 102, terminal 105, inner left-hand armature and back contact of relay 107, left-hand armature and back contact of relay 112, winding of relay 111 to grounded battery. The circuits for relays 109 and 111 of connector E are interrupted each time impulse relay of the trunk C is deenergized, and it will be seen that these relays thus control the usual motor magnets to set the switch in accordance with the digit dialed. Relay 36 being of the slow-to-release type does not release its armatures during the sending of impulses. I

Each time relay 109 deenergized a circuit for primary magnet 115 will be completed over the following, path:ground, left-hand arn'iature and back contact of relay 109, inner armature and front contact of relay 110, winding of relay 116, back contact and armature of relay 117, back contact and armature of relay 112, winding ot primary magnet 115, side switch wiper 119 in its first position to grounded battery. Belay 116 is energized during the transmis sion of impulses, and at its armature and alternate contact completes a circuit for escape magnet 121. Relays 110 and 116 are of the slow-to-release type and do not re lease during the sending of impulses. Primary magnet 115 will thus be energized over this circuit a number of times corresponding to the digit dialed, and will step the brushes to the level containing the terminals of the wanted line. 7

After the transmission of the last impulse of the tens series, impulse relay 109 remains energized, thus opening the circuit for relay 116, which in releasing opens the circuit for escapement magnet 121. Escapement magnet 121 upon deenergization moves the side switch brushes into position 2.

.111 response to the units series of impulses, impulse relay 109 of connector E will again be intermittently energized and deenergized in response to the impulses transmitted by sender S, causing secondary magnet 120 to move the brushes 130, 131 and 132 into engagement with the terminalsv of the desired line. b

Escapement magnet 121 will be energized as heretofore described and if after the units series of impulses has been sent the desired line is idle, terminal 135 being ungrounded, escapement magnet 121 will be deenergizcd and in so doing will move the side switch brushes into position 3. In position 3 of the lie switch brushes, relay 128 is energized over a circuit extending through side switch brushes 129 and 119.

lVhen sender S returns to normal, relay 18 of cord circuit B will be deenergized thus restoring the continuity of the cord circuit and removing battery from the tip and ring of cord circuit B, whichresults in the deenergization of relay 23, and in turn relay 28. Relay in deenergizing restores battery and ground to the inner section of the trunk circuit and relay reconnects the ringing rela Slacross the trunk. Supervisory relay 10 again energized causing supervisorylamp 15 to li ht, which is an indication to the operator that the called line is idle. Im-

pulse relay 3:") is held energized, after the impulses have been .ent through the outer left-hand normal contacts of relay 23 and front contact and left-hand armature of re lay 34-.

The operator then restores key 14-v to normal and thereafter actuates ringing key 19, which results in the energization of the bridged ringing relay 31 over the following path :ground, upper alternate contacts of ringing key 19. tip of plug 20, tip of jack 21, upper left-hand winding of repeating coil 28. winding of relay 31, condenser 32, in-

ner left-hand armature and back contact of relay lower left-hand winding of repeat ing coil 28. ring of 21, ring of plug 20. and lower alternate contacts of ringing key 14 to source of ringing current Belay 31 upon energization completes a parallel circuit for the energization of relays 28, 24 and 39. Relay 28 thereupon attracts its armatures and disconnects battery and ground from the trunk circuit during the time that ringing key 19 is actuated. Relay 24 in operating locks up under the control of sleeve relay 22, thereby interrupting the circuit for relay which will not respond to ringing current and was. therefore notoperated when ground at retardation coil 108.

control relay 37, and completes a circuit to hold relay 109 energized. Relay 111 in deen'e'rgizing completes a circuit for ringing relay 11 8. Belay 37 looks up over a path including its left-hand armature and front contact, back contact and left-hand armature of relay 41-0 and front contact and armature of sleeve relay 22. Through the front contact and right-hand armature of relay 37, ground .is intermittently connected to relay 39 Which controls the automatic application of ringing current to the called line after the operator restores ringing key 19. This operation is as follows relay 39 responds to interrupter 50'; each time it becomes energized it provides at its outer right-hand armature'and front contact a substitute circuit for relay 109 and at its inner right-hand armature interrupts th circuit of relay 111; the circuit for ringing relay 118 is thus in termittently opened, so that during the'socalled silent period relays 109 and 111 are energized and during the ringing period relays 39, 109 and 118 are energized. The circuit for impulse relay 109 upon energiza tion of relay 39 is as follows :gr0und, front contact and outer right-hand armature of relay 39, upper right-hand Winding of repeating coil 27, brush 101, terminal 104, outer'left-hand armature and back contact of relay 107, Winding of relay 109 to grounded battery. Each time the circuit of relay 39 is interrupted by interrupting device 50, relay'111 is energized over the path previously traced and the circuit for ringing relay 118 of connector E is thereby opened at the armature and back contact of relay 111.

Upon the response of the subscriber at station F, during the time that relay 118 is deenergized, relay 107 is energized through the called subscribers substation circuit F and a circuit for relay 410 of trunk circuit C is completed over the following path grounded battery, Winding of retardation coil 148, left-hand winding of relay 107, tront contact and inner left-hand armature of relay 107, terminal 105, brush 102, lower right-hand winding 01 repeating coil 27, in her righthand armature and back contact right-hand armature of relay The lefthand Winding of relay is shunted by the Relay 10 attracts its armatures and is then held up through its tWo windings in series by bat- "tery and ground supplied by coils 148' and 108. Relay 10 in operating interrupts at its left-hand armature and back contact the holding circuit for relay 37, thereby causing the disconnection of the ringing current, and at its left-hand armature and front contact establishes a circuit for relay -28. Relay 28 is then held locked up under the control of sleeve relay 22. Relay 28 in energizing disconnects battery and ground from the inner section of trunk C, resulting in the deenergization of supervisory relay 10 and the extinguishing of supervisory lamp 15, which is an indication to the operator that the called subscriber has answered.

When relay 107 becomes energized, relays 109 and 111 becomes deenergized, but relay 110 is provided With a substitute holding circuit through the right-hand armature and contact of relay 107.

Upon completion of conversation and the restoration of the receiver tothe switchhook by the subscriber at station F, relay 107 deenergizes thereby again connecting relays 109 and 111 to the trunk circuit. Relay 107 is of the marginaltype'and will not remain energized in series with the Windings'of relay 40. Relay 110 is then held up through the left-hand armature and front contact of relay 109. When relay 107 deenergizes due to the subscriber at-station F hanging up, relay 410 is also deenergized, which interrupts the holding circuit for relay 28, thereby connecting battery and ground to the inner section of trunlrC. Supervisoryrelay 10 is thereupon energized and lamp lights, indicating to the operator that conversationis completed. Withdrawal of plug from jack 21 restores all relays in the trunk circuit to normal and releases relays 109 and 110 in the connector circuit Which closes a path for the release magnet thereof, thereby causing the release of the connector in the manner Well known. The system is ready for another call.

If the selected line is busy ground will be present'on terminal 135. This ground holds up escapement magnet 121 through the normal contact of relay 116, thus preventing the side switches from being moved out of position 2, and also completes a cir cuit for relay 112, Which upon energizing causes a busy signal to be connected to the line of the calling subscriber, indicating that the called line is busy. Relay 40 of trunk circuit C is'energized as before by the initial unbalancing of the currents flowing through its windings by the shunting of its lefthand Winding and after attracting its armatures it is held up over a path Which may be traced from grounded batteryfwinding of relay'l09, back contact and outer lefthand armature of relay 107, terminal 104, brush 101, upper right-hand Winding of repeating coil 27, outer right-hand armature and back contact of relay 39, left and righthand Windingsof relay 40, front contact and left-hand armature of relay 36, back contact and inner right-hand armature of relay 39, lower right-hand winding of re pcating coil 2?, brush 102, terminal 105, inner left-hand armature and back contact of relay 107, left-hand armature and front contact of relay 112, and in parallel through the secondary winding of busy signal device 150 to ground and winding of retardation coil 108 to ground. Relay 40 in operating establishes a circuit for relay 28, said circuit including the left-hand armature and front contact of relay 40 and the armature and front contact of sleeve relay 22'. Relay 28 in operating disconnects battery and ground from the inner section of trunk C and prevents the supervisory lamp from lighting. Removal of plug 20 from jack 21 restores all relays and the automatic switches to normal in the manner heretofore described.

It vill be noted from the above description that by sending the impulses over the talking conductor of the trunk circuit, instead of the sleeve conductor, which is frequently done, there is no moment when there is not a busy test on the sleeve of the jack so that there is no probability of an operator plugging into a busy trunk which might occur if she should test the sleeve of the jack at the instant when the circuit for the impulse relay was interrupted by the impulse sender.

What is claimed is:

1. In a telephone exchange system, a trunk circuit divided into inner and outer sections, a repeating coil for uniting said sections inductively, a cord circuit connected with the inner section, an impulse sender, means responsive to the initial actuation of said impulse sender for connecting said impulse sender to said cord circuit, automatic switches accessible to the outer section of said trunk, and means for repeating impulses received over a portion of one of the talking conductors of the inner section to the outer section for operating said switches.

2. In a telephone exchange system, a trunk circuit comprising a pair of talking conductors, inductive means connected in and electrically dividing the talking conductors into inner and outer sections, a cord circuit connected with the trunk circuit, an impulse sender, means for connecting the impulse sender with the cord circuit, a relay operated in response to the initial actuation of the impulse sender and thereafter controlled by the impulse sender over one of the talking conductors of the inner section for repeating impulses to the outer section, and means for maintaining said relay energized atter said impulse sender has been operated until said cord circuit is disconnected from said trunk circuit.

8. In a telephone exchange system, a

trunk circuit comprising a pair of talking conductors, inductive means connected in and electrically dividing the talking conductors into inner and outer sections, a source of current normally connected to the inner section of said trunk, a cord circuit connected with the trunk circuit, supervisory means in said cord circuit actuated by said source of current, an automatic switch accessible to the outer section of said trunk, an impulse sender, means for connecting said impulse sender with said cord circuit, a relay in said trunk circuit controlled by the impulse sender over one of the talking conductors of the inner section for repeating impulses to the outer section to control said automatic switches, and means responsive to the actuation of said impulse sender for disconnecting said source of current and for connecting said impulse sender in operative relation to said relay.

4. In a telephone exchange system, a trunk circuit divided into inner and outer sections, a repeating coil for uniting said sections inductively, a cord circuit connected with the inner section, supervisory means in said cord circuit, a source of current normally connected to the talking conductors of the inner section of said trunk for actuating said supervisory means, an impulse sender, means tor connecting said impulse sender with said cord circuit, an impulse repeating relay controlled by said impulse sender over a portion of one of the talking conductors of the inner section of i said trunk, normally disconnected from said talkiing conductor, means for associating said repeating relay with said talking conductor and for disconnecting said source of current during the sending of impulses, an automatic switch accessible to the outer section of said trunk and controlled by said repeating relay and means for maintaining said trunk busy during the sending of impulses.

,5. In a telephone exchange system, a trunk circuit comprising a pair of talking conductors, inductive means electrically dividing the talking conductors into inner and outer sections, an automatic switch accessible to the outer section, a called line, a cord circuit connected to the inner section, an impulse sending device, means for connecting the impulse sending device with the cord circuit, an impulse repeating relay associated with the inner section oi said trunk circuit responsive to impulses from said impulse sending device over said cord circuit and one of the talking conductors o1 the inner section of said trunk for repeating impulses over the outer section of said trunk to cause said automatic switch to seize the called line, a supervisory signal associated with said cord circuit, and means for actuating said supervisory signal upon the response of the subscriber of the called line.

6. In a telephone exchange system, a. trunk circuit comprising a pair of talking conductors extending from a manual switchboard to an automatic exchange, a called line at said automatic exchange, a cord circuit at the manual switchboard, an impulse sender for said cord circuit, an impulse repeating relay associated with the inner sectionrof said trunk circuit adapted to set switches in the automatic exchange in accordance with the digits dialed, said repeating relay controlled over a portion of said cord circuit and of one of the talking conductors of said trunk circuit, automatic ringing means for signalling said called line, operator controlled means for initiating the application of said automatic ringing means, a supervisory signal in said cord circuit, and means for actuating said signal when said called line is idle.

7. In a telephone exchange system, a manual switchboard, an automatic exchange, a trunk circuit comprising a pair of talking conductors extending between said switchboard and said exchange, a called line at said automatic exchange, a station for said called line, a cord circuit at said manual switchboard, an impulse sender, an impulse repeating relay asso ciated with the inner section of said trunk circuit adapted to operate switches in said automatic exchange in accordance with the digits dialed said repeating relay being controlled over a portionof said cord circuit and one of the talking conductors of said trunk circuit, automatic ringing means for signalling the station of said called line, a supervisory signal in said cord circuit, means for energizing said supervisory signal during the application of said automatic ringing and means for deenergizing said supervisory signal upon the response of the subscriber of said station.

8. In a telephone exchange system, a

' trunk circuit comprising a pair of talking conductors, inductive means connected in and electrically dividing the talking conductors into inner and outer sections, a cord circuit connected with the inner section of said trunk circuit, an impulse sender, means "for connecting the impulse sender to the cord circuit, an automatic switch accessible to the outer section of said trunk circuit, a

subscribers line to which said automatic switch has access, an impulse repeating relay responsive to impulses from said impulse sender over a portion of one of the talking conductors of the inner section of said trunk for operating said 'iautomatic switch, to connect said cord circuit with said called line, a supervisory signal in said cord circuit, means for actuating said supervisory signal when said 'subscribers line is idle, and means for preventing actuation of said supervisory signal when said line is busy.

9. In a telephone exchange system, a trunk circuit, a cord circuit connected to said trunk circuit, an automatic switch, a called telephone line accessible to said automatic switch, means associated with said cord circuit for transmitting electrical impulses over a portion of one of the talking conductors oi said cord circuit and said trunk circuit to cause said automatic switch to seize said called line, a source of machine ringing current, means for initiating the application of said ringing current to said called line, a supervisory relay associated with said cord circuit, means for energizing said supervisory relay during the application oi said machine ringing current to said line, and means for deenergizing said supervisory relay upon the responseof the subscriber of said called line. I 10. In a telephone exchange system, a calling and a called line, means including an operators cord circuit, an inductively divided trunk circuit, and an automatic switch for interconnecting said lines, an impulse sender forsetting said switch, a supervisory signal for said cord circuit, a source of current normally connected to one section of said trunk circuit for controlling said supervisory signal, a source of machine ringing, a key controlled by the operator for initiating the application of the machine ringing to the called line, means controlled by said sender ifor disconnecting said source of current during the transmission of impulses, and means cont-rolled by said key for disconnecting said source of current during the time that the key is actuated. I 7

In witness whereof, I hereunto subscribe my name this 24th day of December, A. D. 1919.

ARTHUR RAYNS'FORD. 

